Tracking CA's Trash: Street Sweeping & Curb Inlet Screen Evaluation

Tracking CA’s Trash: Street Sweeping & Curb Inlet Screen Evaluation

Evaluation of Street Sweeping and Curb Inlet Screens as Measures to Control Trash in Stormwater

  • 21 March 2017
  • Author: Geoff Brosseau
  • Number of views: 591
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This report is one of three technical reports of Tracking California's Trash – a Proposition 84 Storm Water Grant Program project funded in large part by the State Water Board.  BASMAA and its project partners – 5 Gyres, City of Fremont, City of Oakland, City of San Jose, San Mateo Countywide Water Pollution Prevention Program, and Santa Clara Valley Urban Runoff Pollution Prevention Program provided the match funds.

The primary objectives of the project were to:

  1. Develop and test scientifically sound and cost-effective stormwater and receiving water trash monitoring methods that allow agencies to measure sustained, long-term water quality improvements over time.
  2. Fill critical information gaps on the effectiveness and costs/benefits of implementing specific stormwater BMPs (e.g., street sweeping) that address trash.

This report presents an evaluation of effectiveness and cost of two best management practices for trash – street sweeping and curb inlet screens.  

  • Street Sweeping – Scientists and engineers have conducted numerous studies designed to quantify the effectiveness of street sweeping at removing various pollutants over the last 30 years.  The vast majority of these studies have focused on evaluating the effectiveness of different types of street sweepers in removing sediments and pollutants associated with sediment, such as PCBs, metals (i.e., mercury, copper, lead, zinc, etc.), petroleum products, chlorinated and organophosphate pesticides, and polybrominated diphenyl ethers (PBDEs).  In contrast, few have focused on their effectiveness in removing trash from street surfaces.  Although lessons learned from studies focused on sediment and other pollutants may assist practitioners in evaluating the trash control benefits of street sweeping, there are considerable differences in densities and other characteristics of these substances.  
  • Curb Inlet Screens – Partial-capture devices are treatment devices that have not been certified/approved as full capture systems, but have some level of trash reduction benefit.  Curb inlet screens are one type of partial capture device.  Curb inlet screens are perforated screens or evenly spaced bars that are designed to fit outside or immediately within the storm drain curb opening.  Inlet screens may be fixed or retractable.  Retractable screens open either manually or hydraulically when a storm flow/volume is detected.  Since curb inlet screens block trash and debris from entering the storm drain inlet or storm drain, trash remains in the street and is removed by regular street sweeping or other measures.  

Monitoring was conducted at seven study areas located in the cities of Fremont, Oakland, and San Jose, California.  Monitoring activities included the removal of trash from streets, sidewalks, and drain inlets in three of the seven study areas (i.e., quantitative study areas) immediately before and after street sweeping events.  The collected trash was quantitatively characterized in terms of weight, volume, and item counts.  Quantification events were supplemented with qualitative On-land Visual Trash Assessments (OVTAs), which were conducted at all seven sites before, after and between street sweeping and rainfall events.

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